1. Field of the Invention
The present invention relates to a document image process achieved by a digital image processing system such as an image scanner, a facsimile, a digital copier or the like, and more particularly, to a method and device for enlarging or reducing an original image to obtain a copy image changed in magnifying power or magnification.
2. Description of the Related Art
In a conventional digital image processing device employed in a digital copier, which can transform an original image into electrical signals by way of a photo-electric transducer well-known as an image sensor, such as a CCD sensor, the device essentially requires a magnification adjusting function for enlarging or reducing the original image so as to obtain an enlarged or reduced copy.
The conventional magnification adjustable device employed in an analog copier can adjust the magnification of the image by means of a magnifying power controllable lens which is operated through a lens driving assembly that is complicated in construction. With the conventional technique mentioned above, it is an obstacle to miniaturize the product in size from view of the recent technical tendency. Moreover, in case the image data is received by the photo-electric transducer, such as a CCD imaging sensor, the position of the spatially arranged sensor as well as the number of pixels inputted from each sensing line to be scanned by the sensor are constantly fixed with a result that a desired magnification effect cannot be assured in accordance with the change of the magnifying power (magnification) of the lens. In particular, when the image data is input through a contact image sensor (CIS), the desired magnification of the image effected through a self-focusing lens is unrealizable because the lens practically corresponds to the number of the pixels at a ratio of 1:1.
For this reason, it is considered that the magnification function of the image processing system is embodied by way of an electrical process method, particularly a digital signal processing method.
The enlargement or reduction of the image, which is carried out with a positive number magnification ratio, for example, one time, two times, three times, . . . , n times with the vertical and horizontal dimensions of the original (considering the area of the original, one time, four times, nine times, . . . , n.sup.2 times), will be simply achieved by appropriately dividing or multiplying the clock signals.
In the magnification ratio required for an image scanner, a facsimile, a digital copier or the like, the magnification of the aforementioned positive numbered times as well as the enlargement or reduction and document size A4 to a size B4 or B5 must be simply established. In this case, a fine adjustment in magnification ratio must be assured at regular intervals of 1%.
In the conventional techniques mentioned above, however, there are drawbacks because the employment of the magnifying lens for changing the magnification of the image is unsuited for the image processing system with the CCD image sensor, and the construction of the system is greatly complicated. Alternatively, the image magnification adjusting function can be easily embodied by way of a software technique. In this case, however, there is a problem in that real time processing in the system using the pixel output speed above several MHz is difficult. For real time processing, a processor having an operating frequency higher than the pixel clock frequency is required, so a cost of embodying the system is greatly increased.
In order to solve the problems, a technique where the pixel output frequency is divided or multiplied suitably is proposed in, for example, Japanese patent publication No. 63-125055 issued to Cannon Co. Ltd. With the technique described in the patent, it is very difficult (1) to establish the fine magnification of the image in a unit of 1% and (2) to assure an accuracy timing for the magnification conversion.
Accordingly, an object of the present invention is to provide a method and device in which magnification of an image can be converted or adjusted to a unit of 1%.
Another object of the present invention is to provide a method and device for adjusting the magnification ratio of an image, which can arbitrarily select the pitch (the number of output pixel per inch) of output pixels in a horizontal (main-) scanning direction and the pitch (the number of output lines per inch) of output lines in a vertical (sub-) scanning direction.
To achieve the above objects, according to the present invention, there is provided a method for adjusting the magnification of an image, the method including the steps of:
designating image input parameters and producing control factors when a desired magnification of an original image is set: scheduling function information required for the desired magnification processing in main and sub-scanning directions into a form of a look-up table by using the image input parameters and control factors; and carrying out a pixel inserting process and a scan line inserting process at a predetermined interval when the enlarging magnification of the original image is set depending on the function information and, otherwise, carrying out a pixel removing process and a scan line removing process at a predetermined interval when the reducing magnification of the image is set by the function information.
According to a preferred embodiment of the invention, the step of scheduling the look-up table includes: sequentially providing magnification conversion address x' of the main-scanning direction from a main-scanning magnification LUT address i and storing the magnification conversion address into a main-scanning magnification look-up table; and calculating a scanning position corresponding to a sub-scanning magnification from a sub-scanning magnification LUT address j to determine a relative scanning position 6 of a subsequent scanning line in order and storing the determined position into a sub-scanning magnification conversion look-up table.
According to another embodiment of the invention, the step of processing the magnification includes: selecting any block of at least logically blocked memory banks as an image data storage memory and selecting the other block as a magnification processing memory in synchronous with a line scanning start signal L-CNT; storing the image data in the image data from the magnification processing memory to interpolate the data by way of a predetermined interpolation method so as to accomplish the desired magnification of the image in the main-scanning direction; and shifting a phase of a motor on the basis of the magnification processing function information of the sub-scanning direction to control a position of a sensor module so as to complete the desired magnification process in the direction.
The present invention is directed also to a device for adjusting magnification of an image, and includes: magnification processing means of a main-scanning direction for inserting or removing data related to at least one pixel to or from input pixel data on the same scanning line at a predetermined pixel interval in accordance with horizontal magnification ration; and magnification processing means of a sub-scanning direction for inserting or removing data related to at least one scanning line or from pixel data of each scanning line at a predetermined line interval in accordance with a vertical magnification ration.
According to the invention, the magnification processing means of the main-scanning direction includes a first address generating means for generating the image registration address to store input image data IMG-IN in synchronous with a pixel clock signal P-CLK; a second address generating means for generating the reading magnification address to execute the magnification process in accordance with the horizontal magnification in synchronous with a magnification clock signal CON-CLK; first and second memory means for alternatively storing the input image data IMG-IN; a control means for dividing the line scanning start signal L-CNT by 1/2 to simultaneously produce a storage control signal for storing the scanned image data and a reading control signal for accessing the first and second memory means so as to execute the desired magnification adjusting or converting process; a magnification adjustable means for adjusting the magnification of the image data provided from the first or second memory means by way of a predetermined interpolation method; and means for determining data transferring paths between the first or second memory means and the first address generating means and between the second or first memory means, the magnification adjustable means and an input data transferring path on the basis of the storage control signal and reading control signal supplied from the control means.
According to the invention, the second address generating means includes a look-up table memory means for storing the magnification address data of the main-scanning direction from a central processing unit (CPU) in a form of the look-up table; and means controlled by a control signal LUT-CS from the CPU for defining a path throughout which the main-scanning magnification LUT address data and magnification address data of the main-scanning direction are transferred.
According to still another feature of the invention, the second address generating means includes an exclusive arithmatic logic unit (ALU).
According to still yet another feature of the invention, the magnification adjustable processing means of the sub-scanning direction comprises a third address generating means for generating the magnification address of the sub-scanning direction in synchronous with the line scanning start signal L-CNT; a relative position storage memory controlled by a predetermined control signal YLUT-CS for storing a relative scanning position data .delta. related to a subsequent line into an area of the memory designated by the sub-scanning magnification address; and a control means for controlling a phase shift of a motor on the basis of the relative position data .delta.. These and other objects, features and advantage of the present invention will be apparent from the following description taken with reference to the accompanying drawings.